1. Field of the Invention
This invention relates to an integrally shaped plastic closure, having a lower element and a cap, which is connected by a hinge, which creates a snap effect. Here, the cap and the lower element of snap closures have curved casing walls, which are preferably shaped as circular or oval cylinders and are located vertically above each other in the closed state. Such plastic closures, which are applied to plastic containers in particular, essentially differ, besides in the design shape, with respect to the embodiment of the hinge creating the snap effect.
2. Description of Related Art
One of the earliest plastic snap closures is disclosed in Palazzolo, U.S. Pat. No. 3,135,456. A closure, having a cap and lower element, as well as a movable element connecting the two elements, can be made in one piece of plastic. In this case the hinge is formed by the movable element, which is delimited with respect to the cap, as well as with respect to the lower element, by a film hinge extending in the shape of an arc. The two arc-shaped film hinges approach each other from the side of the strip-shaped movable element in the direction toward the center, and move apart from there in the direction of the other movable element. Thus, the two arc-shaped film hinges approach each other toward the center, but do not touch each other. Thus a flat movable element remains between the cap and the lower element, which can be moved over two totally separated pivot axes. Thus, two independent tilt movements occur during respectively opening or closing of the closure, which causes a closing movement which cannot be coordinated. During opening, the center of the movable element is compressed because of the casing walls formed as circular or oval cylinders, while the longer, lateral movable surfaces are placed under a relatively large tensile stress. Because the casing walls of the closure are also made of plastic and have elasticity, a deformation of one or both casing walls of the cap, or respectively the lower element, occurs during the respective opening or closing of the closure. This principle disclosed here was only recognized again later and was again realized in various different snap closures.
Such a closure on a container is represented in German Patent Reference DE-A-19 60 247, wherein the casing wall is specially designed for creating this spring effect. This unusual snap hinge technology was in absolute contrast to the system which had been customary up to that time, wherein the closure was formed by a spiral spring element, wherein the spiral spring was either stretched or compressed during opening, because of which there are three hinges. The main hinge is the connection between the cap and the lower element, while the spring element is connected via two film hinges, extending parallel with the main hinge, on the one side to the cap, and on the other side to the lower element. German Patent Reference DE-A-18 08 875 discloses such a film hinge closure. This reference teaches no use of the deformation of the casing walls of the closure.
European Patent Reference EP-A-0 056 469 is in contrast thereto, wherein the principle of the system of U.S. Pat. No. 3,135,456 is taken up again because the curved film hinges only approach each other. European Patent Reference EP-A-0 056 469 discloses the same system, wherein the limiting film hinges run together towards the center into a common main film hinge. Thus a snap hinge is formed having two lateral tensile elements with an approximately triangular shape and oriented toward each other with their tips, and from there continue to run into a common main axis. Since the movable portion between the cap and the lower element is reduced to an absolute minimum, an exact closing movement around the so-called main axis results, but this unavoidably leads to considerably increased forces in the snap hinge. In principle the two lateral triangular stretch elements would be too short, and accordingly the casing walls, which are curved in an arc, need to be relatively strongly deformed. This mode of function is correctly described for the first time in this document.
The tensile elements arranged laterally of the main axis are bordered by film hinges. The increased tensile stresses lead to these film hinges being overextended during the first closing of the closure, and therefore the tensile elements are curved outward in the form of an arc with respect to the casing walls. This was esthetically unsatisfactory and also led to defects again and again, since the overextended film hinges were extremely sensitive to shearing forces. Accordingly, further film hinges were developed which had tensile strips in place of the triangular lateral tensile elements, which were housed in recesses and extended in the shape of an arc in the open state of the closure. These tensioning strips made a transition directly into respectively the cap or the lower element without film hinges. Accordingly, there were no film hinges which could be overextended, and even after multiple uses the tensioning strips remained extending practically in the plane of the casing walls. However, the principle of the elastic deformation of the casing walls during opening and closing of the closure was employed here, too. This system is known from European Patent Reference EP-A-0 291 457.
Finally, a solution has become known from European Patent Reference EP-A-0 640 167, which again returns to the old system taught by U.S. Pat. No. 3,135,456 wherein the two pivot hinge axes, formed by the so-called xe2x80x9ccurved linesxe2x80x9d and extending at a distance from each other, lead to a closure, whose closing movement takes place in a manner not rationally foreseeable. An element controlling the closing movement was attached in the area between these two film hinges. This is a so-called tilt element with two defined contact surfaces which, in a defined movement, initially rest against the lower element, whereupon a first pivot movement around a first pivot axis takes place, after which the second pivot movement then takes place between the support element and the cap. The same takes place in the reverse order when opening the closure. Although the support element described here leads to an improved sequence of movements, it does stiffen the closure in exactly the critical area of the casing walls which must be absolutely deformable. The tensile stresses on the lateral tensile elements are again increased by this. This has the positive result of an increased snap effect and the negative result that the lateral tensile elements also often tear in the area where they are connected respectively to the lower element or the cap. Tears were also discovered along the reinforced tilt element.
A snap hinge in accordance with U.S. Pat. No. 3,135,456 has recently become known from U.S. Pat. No. 5,642,824. In a change of the variation in accordance with European Patent Reference EP-A-0 640 167, the turn-out movement of the intermediate element between the two arc-shaped film hinges is realized by a bulging contact surface on the lower closure element. Thus it is achieved that the intermediate element, which is inwardly arched in the open state, rests on the bulging contact surface during closing. This same functional effect leads to the same tear formation in the central area at both film hinges.
Again based on U.S. Pat. No. 3,135,456, and taking into consideration the prior art acknowledged here, it is one object of this invention to create a plastic snap hinge closure such as is known from U.S. Pat. No. 3,135,456, which is no longer overextended in the transition area between respectively the movable portion of the cap or the lower element, and accordingly no longer tends to tear.
This object is attained by means of an integrally shaped plastic closure with the following specification and claims.
Due to the design of the plastic closure proposed here, the snap effect is no longer achieved by means of the deformation of the casing walls alone, such as in connection with the embodiments in accordance with U.S. Pat. No. 3,135,456 and European Patent Reference EP-A-0 056 469, for example, but also not only by means of the classic spiral springs such as disclosed, for example, in German Patent Reference DE-A-18 08 875, instead, a symbiosis of these two systems is here disclosed for the first time.